with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows multiple peaks
with a duration of about 50 sec. The peak count rate
was ~4400 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 07:13:01.8 UT, 82.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 316.22890, 32.13574 which is equivalent
to:

RA(J2000) = 21h 04m 54.94s
Dec(J2000) = +32d 08' 08.7"

with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 116 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.50 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.5
(+2.84/-2.37) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White
filter starting 86 seconds after the BAT trigger. No credible
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image does not cover the XRT error circle. The 8'x8'
region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about
18 mag. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.21.
Burst Advocate for this burst is D. Kocevski (dankocevski AT gmail.com).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

with an uncertainty of 1.7 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.

If the light curve continues to decay with a power-law decay index of
2.21, the count rate at T+24 hours will be 7.1 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x
10^-14 (4.1 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00724438.
This circular is an official product of the Swift-XRT team.

GCN Circular #20214
V. Sharma, D. Bhattacharya and V. Bhalerao (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data showed clear detection of GRB161129A (Swift BAT detection: S. Barthelmy et al., GCN Circ. 20210) in the 40-200 keV energy
range. The light curve shows multiple peak structure at 07:12:06.0 UT, after 27 secs of the Swift Trigger. The measured peak count rate is 170.205 counts/sec
above the background in combined data of four quadrants, with a total of 2160.0 counts. The local mean background count rate was 377.79 counts/sec. Using
cumulative rates, we measure a T90 of 34.06 secs.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes
across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

GCN Circular #20215
E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin
(Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko
(IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of 161129A (Kocevski et al., GCN 20210) with
Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory.
We obtained several images in R filter starting on 2016-11-29 (UT)
12:51:12. Within enhanced XRT position (Beardmore et al. GCN 20211) we
detected optical source which is absent in USNO-B1.0 but barely visible
in DSS2 (red). At the moment we can not say anything about the source
variability. The source might be a superposition of the afterglow and a
host galaxy. Preliminary photometry of the source is following

GCN Circular #20216
S. Klose and B. Stecklum (both Thueringer Landessternwarte Tautenburg)
report:
We imaged the field of GRB 161129A (Kocevski et al., GCN 20210) with the
Tautenburg Schmidt telescope equipped with the prime focus CCD camera.
Observations were performed at a midtime of 16:41 UT (November 29).
Inside the enhanced XRT error circle (radius 1.7 arcsec; Beardmore et al.,
GCN 20211) we find a faint source at coordinates RA, Decl. (J2000) =
21:04:54.53, 32:08:05.9 (+/- 0.5 arcsec). Using the USNO B2 star at
coordinates RA, Decl. (J2000) = 21:04:54.65, 32:08:05.6 as a photometric
reference (Ic = 18.38), we measure for this source a preliminary (Vega)
magnitude of Ic = 20.3 +/- 0.2 mag.
We note, however, that the DSS2 red shows a faint source at the central
position of the enhanced XRT error circle at roughly the same coordinates.
Given that the seeing in our images is about 2 arcsec, and given that our
images are not substantially deeper than the DSS2 red, we cannot decide
whether we see this faint source or a faint transient on top of it. In any
case, at the time of our observations any optical transient was fainter
than about Ic=20.

GCN Circular #20217
N. P. M. Kuin (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU) report on
behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 161129A
86 s after the BAT trigger (Kocevski et al., GCN Circ. 20210).
A source consistent with the XRT position (Beardmore et al. GCN Circ.
20211) is detected in the initial UVOT exposures.
The source is detected in UVOT images at position:

RA = 21h 04m 54.6s (J2000)
Dec = 32d 08' 05.52" (J2000)

with an uncertainty of 0.6" (90% confidence)
Preliminary detections and 3-sigma upper limits using the UVOT
photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

There are low-significance signs of the source in all other filters. Though
the source seems to reach peak brightness around 500s the photometric
errors are also consistent with a constant source brightness up to 10ks.
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.21 in the direction of the burst
(Schlegel et al. 1998).

GCN Circular #20219
O.J. Roberts (UCD), C. Meegan (UAH), and R. Hamburg (UAH)
report on behalf of the Fermi GBM Team:
"At 07:11:39.96 UT on the 29th of November 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 161129A
(trigger 502096303/161129300), which was also detected by
Swift (Kocevski et al., GCN 20210). The GBM on-ground location
is consistent with the Swift position. The angle from the Fermi
LAT boresight is 87 degrees using the Swift position.
The GBM light curve shows a bright burst, with multiple peaks
over a duration (T90) of about 36 s (50-300 keV).
The time-averaged spectrum from T0+4.8 s to T0+45.7 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.13 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 197 +/- 21 keV.
The event fluence (10-1000 keV) in this time interval is
(8.4 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+26 s in the 10-1000 keV band is 5.6 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.
The mask-weighted light curve shows a short spike from ~T0 to ~T+0.2 s,
followed by several overlapping pulses that last until ~T+45 s.
T90 (15-350 keV) is 35.53 +- 2.09 sec (estimated error including systematics).
The time-averaged spectrum from T+0.06 to T+44.58 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.57 +- 0.06. The fluence in the 15-150 keV band is 3.6 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+26.64 sec in the 15-150 keV band
is 3.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
Because the light curve seems to resemble that of a short GRB with
extended emission (Norris et al. 2010), we perform further analysis of the
short spike. Using a 4-ms binned light curve, the lag analysis finds a lag of
4 +/- 3 ms for the 50-100 keV to 15-25 keV band, which is consistent with
that of a short GRB. However, the spectral fit of the short spike
using a simple power-law model gives a power-law index of 1.9 +/- 0.3.
This value is on the softer end of short GRBs, and also softer than all the
initial pulses of those short GRBs with extended emission (Lien et al. 2016).
The power-law index of the spectrum for the rest of the light curve
is 1.53 +/- 0.06, which is harder than the initial spike and thus
unexpected from a short GRB with extended emission.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/724438/BA/

GCN Circular #20223
K. Yanagisawa, D. Kuroda, Y. Shimizu, H. Izumiura (OAO/NAOJ),
M. Yoshida (Hiroshima), K. Ohta(Kyoto), and N. Kawai(Tokyo Tech.)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 161129A (Kocevski et al., GCNC 20210)
in Ks-band with a wide-field NIR camera at Okayama Astrophysical
Observatory (Japan). The camera has an effective aperture of 0.91m.
Observations started from 08:44 UT on 29th November, 93 min after
the BAT trigger, to 09:29 UT. The total exposure of 17.3 min was
successfully obtained.
In our co-add image, we found a faint source at coordinates

R.A.(J2000) = 21:04:54.59
DEC (J2000) = +32:08:05.2,

close to the position reported by Beardmore et al.(GCNC 20211),
and Klose & Stecklum (GCNC 20216).
We measured the source magnitude of Ks = 15.95 +/- 0.14 (Vega).
The calibration was made against 2MASS field stars.

GCN Circular #20242
Tomoki Morokuma and Yuki Sarugaku (Univ. of Tokyo) report on behalf
of=E3=80=80the OISTER collaboration:
We observed the field of GRB 161129A (Kocevski et al. GCN 20210)
with=E3=80=80the 1.05-m Schmidt telescope and KWFC (Sako et al. 2012, Proc.
SPIE=E3=80=808446, 84466L) at Kiso Observatory in Japan. The observations
were
made=E3=80=80in z-band at 2016-11-29 08:15-08:36 (UT; about 1 hour after
the
burst). The flux is calibrated with z-band imaging data for a nearby
SDSS field taken at almost the same airmass as that of the GRB field.
We do not detect any new source within the XRT error circle or at the
position with Swift/UVOT and other telescopes' detections (e.g., Kuin et
al. GCN 20217) and the upper limits are as follows.

A finding chart is posted at this URL:
http://www.astro.ku.dk/~malesani/GRB/161129A/GRB161129A.png
Given their small separation (1.4"), these objects may be blended in
images with coarser spatial resolution. Source A (with a magnitude R =
21.6) is consistent in flux and position with the faint smudge visible
in the DSS red, previously noted by Mazaeva et al. (GCN 20215) and Klose
& Stecklum (GCN 20216).
Source B is extended, and is consistent with the position reported for
the optical afterglow by Kuin et al. (GCN 20217) and Kuroda et al. (GCN
20218). We propose that source B is (dominated by) the host galaxy of
GRB 161129A. We further note that the cumulative magnitude of the
complex (objects A+B) is R ~ 21.2, which is significantly fainter than
previous reports (e.g. Kuroda et al., GCN 20218; Mazaeva et al., GCN
20224), thus firmly establishing the presence of a fading optical
afterglow for GRB 161129A. Photometry was computed against the values of
the two USNO-B1.0 stars as listed by Mazaeva et al. (GCN 20215).

GCN Circular #20245
=E2=80=8BZ. Cano (IAA-CSIC), D. Malesani (DARK/NBI and DTU Space), A. de
Ugarte
Postigo (IAA-CSIC, DARK/NBI), L. Izzo, C. C. Thoene (IAA-CSIC) and N.
Castro-Rodriguez (GRANTECAN/IAC/Universidad de La Laguna) report:
We observed the field of GRB 161129A (Kocevski et al., GCN Circ. 20210)
with OSIRIS on the 10.4 m GTC telescope on La Palma (Spain). The
observations started at 19:46:40.9 UT on 05-December-2016 (6.52 days after
the burst), which consisted of 4 x 1200 s spectra using grism R1000B, which
covers the wavelength range 3700-7800 angstroms, with a resolution of
R~1000.
Within the enhanced XRT error region (Beardmore et al. 2016, GCN Circ.
20211) we note the presence of sources A & B detected by Heintz et al. (GCN
Circ. 20244). The spectrum of the extended object (source B) shows a
continuum with a strong emission line that we attribute to the [OII]
3727/3729 doublet at z=3D0.645, as well as weaker emission lines consistent
with being H-gamma and H-delta at the same redshift. We propose this
star-forming galaxy to be the host of GRB 161129A. The spectrum of source
A
displays absorption features of Ca II K and H, Mg I and MgH at z~0,
confirming it is a foreground star and not related to GRB 161129A.